feat(mcp): enhance form UX with default apps and JSON formatter

- Enable all apps (Claude, Codex, Gemini) by default when adding MCP servers
- Improve config label with clearer wording: "Full JSON configuration or use [Config Wizard]"
- Add JSON format button to beautify configuration with 2-space indentation
- Update tests to reflect new default behavior
- Clean up redundant explicit prop passing

This provides a more streamlined experience by enabling all apps out of the box
and making it easier to format JSON configurations.

src/components/mcp/UnifiedMcpPanel.tsx

@@ -197,7 +197,6 @@ const UnifiedMcpPanel: React.FC<UnifiedMcpPanelProps> = ({
           }
           existingIds={serversMap ? Object.keys(serversMap) : []}
           defaultFormat="json"
-          defaultEnabledApps={["claude"]} // 默认启用 Claude
           onSave={async () => {
             setIsFormOpen(false);
             setEditingId(null);